The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An internal combustion engine (ICE) combusts an air/fuel fuel mixture within cylinders to drive pistons, which produces drive torque. Air flow into an ICE engine may be regulated via a throttle and adjustment in throttle area. Adjustment in throttle area alters air flow into the ICE. As the throttle area increases, the air flow into the engine increases. Fuel injection rate is adjusted in addition to adjustment in air flow to provide the air/fuel mixture. Increasing the amount of air and fuel provided to cylinders of the ICE increases torque output of the ICE. Engine control systems have been developed to control engine torque output.
Spark ignition direct injection (SIDI) refers to direct injection of fuel into cylinders of a spark ignited gasoline engine. SIDI allows for improved control of when fuel is injected into a cylinder. In a SIDI engine fuel may be injected at various times during a combustion cycle. This is unlike port fuel injected engines where fuel is injected, for example, into a port and/or intake manifold of an engine and before an intake stroke of a corresponding combustion cycle. The increased control that may be associated with an SIDI engine provides increased horsepower, reduced emissions and knock suppression.
SIDI may be used to operate an engine in a double pulse (split pulse) mode during engine startups to reduce emissions. During the double pulse mode two fuel pulses are generated during a single combustion cycle to provide a total injected fuel mass. The first injection may be provided during or before an intake stroke to provide an initial homogeneous lean mixture in a cylinder. The second injection may be provided late in a compression stroke to provide a rich easily ignited cloud around a tip of a spark plug.
The splitting of fuel injection into two fuel pulses allows for retarded spark timing and a more complete combustion with a leaner overall mixture of fuel and air. This minimizes hydrocarbon emissions while a catalytic converter is below an active operating temperature. The retarded spark transfers energy from a burning charge into heat in the exhaust, which quickly increases a temperature of a catalyst while minimizing passage of unburned hydrocarbons into the catalyst.